Sparking plug.



A. E. HEATH.

SP'ARKING PLUG.

APPLICATION mm nov. 29. |915.

Patented July 31, 1917.

f STATES ARTHUR ERNEST HEATH, 0F LQNDON, ENGLAND.

BPARKING PLUG.

Bpeeication of Letters Patent Patented July 3l 191 7.

Application led November 29, 191,8. Serial No, 134,091,

To all whom it 'may concern.'

Be it known that ARTHUR Enb'nsr HEATH, a subject of the King'of GreatBritain, residin at London, England, has invented certain new and usefulImprovements in. Sparking Plugs, of which the following isA aspecific-ation. The object of myinvention is to construct a sparkingplug for internal conibustion enines in which the central electrode isperi ectly insulated from the metal body or casing, an air space isprovided within the metal body or casingr and in some cases the metalbody and other parts may be provided with holes to allow of a current ofair passing through the air space for keeping the central electrodecool.

, According to my invention I construct the sparkin plug from a tubularmetal body forme with an enlargement or chamber at one end and asmallerchamber at the other eudand with a contraction or neck between the two,an electrode having a 'screw thread atene end and an enlargement orshoulder at the other, an insulator surrounding part of the electrodeand having one vportion of larger diameter than the other or fitting thesmaller chamber and obtaining a seating against the contraction or neckin the metalV body, an'air space within the larger chamber the cap andthe walls of the casing surrounding same being provided or not withholes to allow of a circulation of air within the air space, a sparkingpoint on the central electrode or on a ring hold to lthe metal body by,turningover the end, nuts engaging the central electrode for securingthe cap and electrode and :the bottom insulator to the metal body, und acup shaped insulating cap having its-tubular portion o-V sitioned withinthe enlargement or cham er' of the metal body and acting as aninsulating apron between the metal body and the i central electrode.

My invention will be iclearly understood from the following descriptionaided by the annexed drawings in whih:-

Figure ljista sectional elevation of a sparking plug constructedaccording to my invention.

Fig. '2 is a plan of same. y Fi 3 is a similar view to Fig 1 but showinge insulator held in place y the center electrode I and the` metal bodyand cup shaped insulator provided with means for allowing of a passageof 'air through the air space for cooling pur'roscs, and with thesparking point carried by the central electrode instead of by a washeras in Fig. 1./

Fig. Lvlis an elevation of Fig. 3,

According to my inventiond form the tubular metal body o of the plugwith an enlargement or chamber b at'its top or rear end, and its bottomor front end c, which is screw threaded in the usual way for screwingthe plug into the cylinder, is formed with a contraction o1 neck a inthe forni of a beveled valve seating in its bore situate between thechamber b in the^enlai-ged top end o the plug andthe. borein the smallerbottom end,

The porcelain or other insulator e which surrounds or partly inclosesthe conductor or center electrode f, is formed of two diameters, thelarger end4 of the insulator o fitting within the bore of the front endof the metal body a, to the contraction or neck' The open end of theenlarged chamber b i in the metal 'body o is closed by an insulator cupshaped cap y with its tubular portion h Iextending within the body orshell of the i' metal body a, this extension h acting as an insulatingapron between the shell or metalA body a of the trede j.A

The cap y has a central hole i for the passage of the screw threaded endof the plug and the 'central elecelectrode, and the insulator cap g issecured in position at the top end of the metal body a by a nut j andwashers k on the threaded end of the conductor or electrode f. The

bottom or front end of the electrode f is formed with an enlarged headZ, so that by tightening the nut y' on the electrode f the insulator ecan be drawn into the bore of the metal body a and pressed firmlyagainst the contracted seating al in a gas tight manner, l the insulatore may also be secured and held firm in the plug by means or' a washer mbearing on the outer edge, the end of the metal body a of the plugbeingspun over to receive and retain the washer m and insuintox' e inplace, the washer carrying the sparking point n as in Fig. 1 or I mayform the sparking point on the central electrode, as in Fig. 3, in whichcase the washer is dispcnsed with.

g is a' nut und 1' is a spring washer encircling the cloctrodo f thenut' l] securely fixing the insulator c to the 'electrodo f.

, j* 1s u terminal nut for connecting the usual wres'to tho electrode.

By this construction of plug, the whole of the parts are misil cleaned,und the enlarged chamber b provi es an air space surrounding the end oftheinsulator und a, portion of the conductor so that the heat ofthemetal body of the plug is not communicated to the relain' insulator atthat part, and to u'ther insure the cooling of the electrode f. andinsulator o especially when such a plug is used with aviation andexceptionallyhot engines Iprovic'le holes a in the metal casing a andholes t in the cap g for allowingA of a free crenlation'of air in thespab and between'the cap and the electrode and insulator e and tovfurther enhance this cooling I provide fins u'oii' the 'metal body a sothat' the rush of'air'will assist in the coo1ing.

' maat I claim is:-

unginos comprising; :i tubular metal body :i0

foi-mcd with :m opper cnlni'gcrl chamber und :i lower smaller vhnnilmrwith :i con'- trzuztocl neck hoLWcQn the two chambers, au, insulator oftubular form und of materially' less dnnotcr than the upper'chnmber and35 }',r joc.ting into the latter` the lower portion of the insulatorbeing enlarged and snugly Afitting n. portion of tho woll of the Smallerchamber, :in iusulntiugrcupjshnpetl'cnp fitted into the. upperend of themetal body and de- 40 pending into the chamber around the upper end ofthe said insulator, and :m electrode extending through thc insu|:xto rnml 'upl' minllythrough the cup-shaped insulating cap, the upper portionof tlie electrode being' -15 scre\vthre;ulel and oumiged 'by n n'utwitlil Tui iu the cup of the said cap und alsoibyf'n upper nut havingcoperative bearing l\ vitl1"' thertop 'of the cap",' `a' sparkngpointbeing

